'\" te
.\" Copyright (c) 2004, Sun Microsystems, Inc.  All Rights Reserved.
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.TH SETREUID 2 "Mar 22, 2004"
.SH NAME
setreuid \- set real and effective user IDs
.SH SYNOPSIS
.LP
.nf
#include <unistd.h>

\fBint\fR \fBsetreuid\fR(\fBuid_t\fR \fIruid\fR, \fBuid_t\fR \fIeuid\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBsetreuid()\fR function is used to set the real and effective user IDs of
the calling process. If \fIruid\fR is \(mi1, the real user ID is not changed;
if \fIeuid\fR is \(mi1, the effective user ID is not changed. The real and
effective user IDs may be set to different values in the same call.
.sp
.LP
If the {\fBPRIV_PROC_SETID\fR} privilege is asserted in the effective set of
the calling process, the real user ID and the effective user \fBID\fR can be
set to any legal value.
.sp
.LP
If the {\fBPRIV_PROC_SETID\fR} privilege is not asserted in the effective set
of the calling process, either the real user ID can be set to the effective
user ID, or the effective user ID can either be set to the saved set-user ID
from \fBexecve()\fR (see \fBexec\fR(2)) or the real user ID.
.sp
.LP
In either case, if the real user ID is being changed (that is, if \fIruid\fR is
not  \fB\(mi1\fR), or the effective user ID is being changed to a value not
equal to the real user ID, the saved set-user ID is set equal to the new
effective user ID.
.sp
.LP
All privileges are required to change to uid 0.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, 0 is returned. Otherwise, \(mi1 is returned,
\fBerrno\fR is set to indicate the error, and neither of the user IDs will be
changed.
.SH ERRORS
.sp
.LP
The \fBsetreuid()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value of \fIruid\fR or \fIeuid\fR is less than  \fB0\fR or greater than
\fBUID_MAX\fR (defined in <\fBlimits.h\fR>).
.RE

.sp
.ne 2
.na
\fB\fBEPERM\fR\fR
.ad
.RS 10n
The {PRIV_PROC_SETID} privilege is not asserted in the effective set of the
calling processes and a change was specified other than changing the real user
\fBID\fR to the effective user \fBID\fR, or changing the effective user
\fBID\fR to the real user \fBID\fR or the saved set-user \fBID\fR. See
\fBprivileges\fR(7) for additional restrictions which apply when changing to
UID 0.
.RE

.SH USAGE
.sp
.LP
If a set-user-\fBID\fR process sets its effective user \fBID\fR to its real
user \fBID\fR, it can still set its effective user \fBID\fR back to the saved
set-user \fBID\fR.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.sp
.LP
.BR exec (2),
.BR getuid (2),
.BR setregid (2),
.BR setuid (2),
.BR attributes (7),
.BR privileges (7),
.BR standards (7)
